The comic is referencing composite cables!
The yellow swordsman is speaking in braille* because, as the video cable, he can't verbally speak. He's saying "Composite attack!", BTW.
The white and red swordsmen are speaking in music notes, because they are the audio cables.
The black monster they're fighting is supposed to represent the TVs that use composite cables; Each of its eyes are colored as the sockets, and the swordsmen are all stabbing an eye matching their color.
The comic also has a title text that says "You really have to jiggle it into the socket.", further implying the joke.
The only reason I understood this one was because I used to have a composite TV and a Wii console when I was younger.
*Matthew sure loves to defamiliarize the English language in his comics.
